Cherry tree rootstock named ‘Crawford’

ABSTRACT

A new cherry tree variety suitable for use as rootstock.

Botanical designation: The present invention relates to a new Prunuscerasus L. x (Prunus cerasus L. x Prunus canescens Bois) cherry treevariety.

Variety denomination: The new plant has the varietal denomination‘Crawford’.

BACKGROUND OF THE INVENTION

This invention relates to a new and distinct variety cherry tree. It hasas its (female) seed parent the variety known as ‘Újfehértói Fürtös’(Prunus cerasus) (not patented) and as its pollen parent (male) thevariety known as ‘GiSelA® 6’ U.S. Plant Pat. No 8,954 (Prunus cerasus xP. canescens).

In the field of plant genetics, researchers conduct an extensive andcontinuing plant-breeding program including the organization and asexualreproduction of orchard trees, and of which plums, peaches, nectarines,apricots, cherries, almonds and interspecifics are exemplary. It wasagainst this background of activities that the present variety of cherrytree was originated and asexually reproduced in our experimentalorchard.

PRIOR VARIETIES

Among the existing varieties of cherry trees, which are known to us, andmentioned herein, ‘Újfehértói Fürtös’ (not patented), ‘Hedelfingen’ (notpatented); ‘Bing’ (not patented); ‘GiSelA® 5’ U.S. Plant Pat. No. 9,644and ‘GiSelA® 6’ U.S. Plant Pat. No. 8,954.

ORIGIN OF THE VARIETY

The present variety was developed from a first-generation cross between‘Újfehértói Fürtös’, a Hungarian landrace sour cherry variety, and‘GiSelA® 6’ made in 1998. Seeds resulting from the cross were germinatedin East Lansing, Mich. and planted in Clarksville, Mich. in 2000.Seedlings were selected as candidate rootstocks based on overall planthealth, virus tolerance (Prune Dwarf Virus, and Prunus Necrotic RingspotVirus), and rooting percentage of softwood cuttings. Candidaterootstocks produced by asexual propagation were grafted with‘Hedelfingen’ scion and planted in Clarksville, Mich. Further rootstockselection occurred on the basis of scion qualities to include precocity(early flowering and fruiting beginning the second year after planting)and reduced tree stature measured as trunk cross-sectional area.‘Crawford’ was asexually reproduced through conventional softwoodcutting methods, and grafted with ‘Bing’ scion. The ‘Bing’ trees graftedon the ‘Crawford’ rootstock were planted in Prosser, Wash. and evaluatedfor scion trunk cross-sectional area, tree height, growth habit, flowersper node, crop yield, cropping efficiency, and fruit weight, among othertraits. Cherry tree ‘Crawford’ was selected from this trial.

ASEXUAL REPRODUCTION OF VARIETY

Asexual reproduction of the ‘Crawford’ cherry rootstock was achievedusing the mother plant to obtain rooted liners using conventionalsoftwood cutting procedures, and through meristem culture withcommercial nurseries. Initially, liners were propagated from softwoodcuttings in commercial greenhouses. A subset of these liners was used toestablish a mother block in Clarksville, Mich. The remaining liners weresent to a nursery to make test trees of ‘Crawford’ that were budded withthe scion ‘Hedefingen’. The resulting trees were planted in a trial inClarksville, Mich. A second set of liners was propagated from softwoodcuttings in commercial greenhouses. These ‘Crawford’ liners were buddedwith ‘Bing’ scion to make trees for a trial in Prosser, Wash. The livingtissues (i.e. leaves, stems, buds, flowers and fruits) of the originalmother block plants were observed to be identical to secondary andtertiary vegetatively propagated plants.

STATEMENT OF STABILITY

Asexual propagation as described has demonstrated that the combinationof traits that characterize this tree are fixed and remain true to typethrough at least two successive propagation cycles.

SUMMARY OF THE INVENTION

‘Crawford’ is particularly useful as a rootstock. The variety results indwarf trees with significantly smaller canopy size than traditionalnon-dwarfing rootstocks and significantly smaller than trees on ‘GiSelA®6’ rootstocks. When this variety is used as rootstock for sweet cherry,the fruit can be harvested without using ladders. When used as arootstock for sour cherry the fruit can be harvested by an over the rowharvester that can move continuously down the row instead of beingharvested by a trunk shaking machine that harvests each treeindividually. The variety of the invention also has favorable precocity,which results in a scion variety having flower buds and fruit beginningin years two and three rather than years five or six when traditionalrootstocks are used. ‘Crawford’ was selected as a potential cherryrootstock on the basis of its scion trunk cross-sectional area, treeheight, growth habit, flowers per node, crop yield, cropping efficiency,and fruit weight, among other traits, in two experimental field trials.Scion trees grafted onto this rootstock showed significant reduction intrunk cross sectional area compared to ‘GiSelA® 6’ and a trunk crosssectional area similar to ‘GiSelA® 5’. ‘Crawford’ is suitable forstandard nursery propagation practices for uniform liner production.‘Crawford’ can be distinguished from its parents by the use of SimpleSequence Repeat DNA markers. With primer pair PceGA59, ‘Crawford’ isdistinguished from its parent, ‘GiSelA® 6’ by the absence of the 226base pair (bp) allele; and presence of the 194 bp allele. With theprimer pair PruG4RS, ‘Crawford’ is distinguished from its parent,‘GiSelA® 6’ by the presence of the 172 bp allele.

COMPARISON WITH PARENTS

The new cherry variety may be distinguished from its seed parent,‘Újfehértói Fürtös’, a Hungarian landrace cherry variety in that‘Crawford’ is not a sour cherry (Prunus cerasus) variety and ‘ÚjfehértóiFürtös’ is also not a dwarfing rootstock.

The new variety may be distinguished from its pollen parent, ‘GiSelA® 6’by the following combination of characteristics: using the PceGA59primer pair—the absence of the 226 bp allele; and presence of the 194 bpallele; using the PruG4RS primer pair—the presence of the 172 bp allele;anthocyanin coloration of apex; leaf blade length, shape, and ratio oflength to width; nectary shape; and intensity of anthocyanin colorationof young leaf

COMPARISON WITH KNOWN RELATED CULTIVARS

The new cherry variety may be distinguished from known relatedcultivars, for example the cherry trees named ‘Clare’ and ‘Lake’, by acombination of several characteristics. First, using the PceGA59 primerpair, it is shown that ‘Crawford’ contains the 182 allele (which ‘Clare’and ‘Lake’ lack), and that ‘Crawford’ lacks the 226 allele (which both‘Clare’ and ‘Lake’ possess). Additionally, using the PruG4RS primerpair, it is shown that ‘Crawford’ has both the 192 and 200 alleles,which are not found in either ‘Clare’ or ‘Lake’. Other differences inDNA fingerprint data are shown in Table 2. ‘Crawford’ differs from both‘Clare’ and ‘Lake’ in the presence of pubescence (upper third), leaflength, leaf width, the leaf lower surface texture/pubescence, the leafpetiole length and diameter, the flower inflorescence diameter, fruitshape, and others.

‘Crawford’ may also be distinguished from ‘GiSelA® 6’ by its ploidy.Crawford is believed to be a tetraploid, whereas ‘GiSelA® 6’ is believedto be triploid. Crawford is further distinguished from ‘GiSelA® 6’ inthat, using the PceGA59 primer pair, ‘Crawford’ possesses the 194allele, which ‘GiSelA® 6’ lacks, and using the PruG4RS primer pair,‘Crawford’ possesses the 172 and ‘GiSelA® 6’ does not. Additionally,using the PceGA59 primer pair, it is known that ‘GiSelA® 6’ possessesthe 226 allele, which ‘Crawford’ lacks.

BRIEF DESCRIPTION OF PHOTOGRAPHS

The accompanying photographs display flowers, leaves, and fruits from aself-rooted mother block tree at Clarksville, Mich. in 2005.

FIG. 1 is a photograph of the flowers of CRAWFORD;

FIG. 2 is a photograph of two leaves of CRAWFORD;

FIG. 3 is a photograph of five leaves of CRAWFORD with a ruler to showsize;

FIG. 4 is a photograph of cherries from and a seed from CRAWFORD;

FIG. 5 is a photograph of the young tree of CRAWFORD;

FIG. 6 is a photograph of an older tree of CRAWFORD.

DESCRIPTION OF THE NEW VARIETY

The following is a detailed botanical description of the new variety ofcherry tree, its flowers, foliage and fruit, as based on observations ofvarious aged specimens grown near Clarksville, Mich. with color inaccordance with The Royal Horticultural Society Colour Chart (R.H.S.),2001 edition.

-   Measurement details-   Flowers:    -   -   Inflorescence height.—Measured from where the flower cluster            attaches to the branch to the most distal floral part.        -   Flower diameter.—Measured across the petals in mm.        -   Flower length.—Measured from the bottom of the pedicel to            the most distal flower point (mm).        -   Pedicel.—The stem of an individual flower. It is measured            from the attachment in the bud to the start of the perianth.        -   Peduncle.—A stalk supporting an inflorescence. In these            selections, the cherry flowers within a flower bud all start            at the same base and they the stalk separates into            individual pedicels supporting each flower.        -   Anther color.—Before the anther's dehisce, when they are            still bright yellow and plump.        -   Anther length.—Measured for the longest anther measured from            the top of the perianth tube.        -   Style.—Measured above the swelled ovary.-   Tree:    -   -   Height.—Approx. 10 ft.        -   Diameter.—Approx. 10 ft.        -   Vigor.—Weak.        -   Branching habit.—Spreading.        -   Branching.—Strong.        -   Hardiness.—Cold Resistant.        -   Scion compatibility confirmed.—Bing, Montmorency.-   Stem (trunk):    -   -   Texture.—Rough.        -   Color.—Grey brown 200A.-   One year old shoot:    -   -   Thickness.—Thin.        -   Length of internode (middle third of shoot-mean of 10).—3.2            cm (2.9-4.0).        -   Pubescence (upper third).—Present.        -   Number of lenticels per cm ².—5.        -   Anthocyanin coloration of apex.—Very weak.        -   Position of vegetative bud in relation to shoot.—Slightly            held out.        -   Shape of apex of vegetative bud.—Obtuse.        -   Branching.—Medium.-   Leaves:    -   -   Mature leaf arrangement.—Alternate.        -   Intensity of anthocyanin coloration of young leaf (during            rapid growth).—Weak.        -   Leaf blade shape.—Obovate.        -   Leaf blade:ratio length to width.—1.9.        -   Leaf length-blade only (cm).—9.0.        -   Leaf width (cm).—4.6.        -   Leaf blade angle of apex (excluding tip).—Acute.        -   Leaf blade shape of base.—Obtuse.        -   Leaf blade shape of apex (e.g., acute).—Acute        -   Leaf blade; incisions of margin.—Crenate.        -   Leaf blade.—Depth of incisions of margin: medium.        -   Leaf blade glossiness of upper side.—Medium.        -   Leaf blade.—Pubescence of lower side of apex: medium.        -   Upper surface color (R.H.S.).—137B.        -   Leaf upper surface texture/pubescence.—Smooth.        -   Leaf upper surface venation color (R.H.S.).—138A.        -   Leaf venation pattern.—Pinnate.        -   Lower surface color (R.H.S.).—137C.        -   Leaf lower surface texture/pubescence.—Medium pubescence.        -   Leaf lower surface venation color (R.H.S.).—138C.        -   Petiole.—Presence of pubescence of upper side: present.        -   Petiole.—Intensity of pubescence of upper side: medium.        -   Petiole.—Depth of groove: shallow.        -   Leaf petiole length (mm).—14.        -   Leaf petiole diameter (mm).—1.4.        -   Leaf petiole color (R.H.S.).—138B and 59A.        -   Leaf.—Presence of nectaries: present.        -   Varieties with nectaries only.—Leaf — predominant number of            nectaries: two.        -   Leaf.—Position of nectaries: base of leaf blade.        -   Nectary color.—Yellow-green.        -   Nectary shape.—Reniform.        -   Leaf stipule frequency.—Present.        -   Leaf stipule length (mm).—10.        -   Leaf stipule width (mm).—2.        -   Leaf stipule shape.—Pointed.        -   Leaf stipule margin.—Serrated.-   Flowers:    -   -   Flowers per cluster.—1 to 4.        -   Fragrance.—None.        -   Bloom date (50%).—Apr. 29, 2016.        -   Inflorescence diameter (cm).—3.8.        -   Flower diameter (mm).—24.        -   Flower length (mm).—27.        -   Petal number per flower.—5.        -   Petal arrangement.—Flat whorl.        -   Petal length (mm).—13.        -   Petal width (mm).—10.        -   Petal shape.—Oval/round.        -   Petal apex.—Round.        -   Petal margin.—Smooth.        -   Petal texture.—Smooth.        -   Petal color when fully opened.—Upper surface (R.H.S.): 155D.        -   Petal color when fully opened.—Lower surface (R.H.S.): 155D.        -   Sepal number.—5.        -   Sepal length (mm).—6.        -   Sepal width (mm).—4.        -   Sepal shape.—Triangle.        -   Sepal apex.—Pointed.        -   Sepal margin.—Serrated.        -   Sepal texture.—Smooth.        -   Sepal color upper (R.H.S.).—138B.        -   Sepal color lower (R.H.S.).—138B with some 59A.        -   Flower pedicel length (mm).—11.        -   Flower pedicel diameter (mm).—1.        -   Flower pedicel angle (degrees).—30.        -   Flower pedicel texture.—Smooth.        -   Flower pedicel color (R.H.S.).—138B.        -   Flower peduncle length (mm).—5.        -   Flower peduncle diameter (mm).—2.        -   Flower peduncle texture.—Smooth.        -   Flower peduncle color (R.H.S.).—138B.        -   Pistils.—Number of pistils per flower: 1.        -   Pistil length (mm).—11.        -   Pistil color (R.H.S.).—149B.        -   Style length (mm).—9.        -   Style color (R.H.S.).—138C.        -   Stigma shape.—Round/indented.        -   Stigma color (R.H.S.).—138B.        -   Stamens.—Number per flower: 26 to 28.        -   Longest filament length (mm).—7.        -   Stamen filament color (R.H.S.).—155D.        -   Longest anther length (mm).—9.        -   Anther color (R.H.S.).—20B.        -   Pollen color (R.H.S.).—17C.        -   Pollen amount.—Moderate.-   Fruit:    -   -   Mature fruit shape.—Cordate.        -   Mature fruit height (mm).—18.2.        -   Mature fruit width 1 (mm).—16.8.        -   Mature fruit width 2 (mm).—18.6.        -   Mature fruit ratio height/width 2.—0.98.        -   Mature fruit weight (g).—4.0.        -   Mature fruit flesh taste.—Sour.        -   Mature fruit skin color (R.H.S.).—187A.        -   Mature fruit flesh color (R.H.S.).—187D.        -   Stone color (R.H.S.).—164D.        -   Stone shape.—Elongate.        -   Stone number.—1.        -   Stone height (mm).—11.1.        -   Stone width 1 (mm).—9.0.        -   Stone width 2 (mm).—7.2.        -   Stone ratio height/width 2.—1.53.        -   Stone weight (g).—0.36.        -   Fruit stem length (mm).—29.-   Market use: Rootstock.

SIMPLE SEQUENCE REPEAT (SSR) MATERIALS AND METHODS

The use of clonally propagated Prunus sp. rootstocks in cherryproduction is increasing as these rootstocks provide reduced tree sizeand precocity. DNA markers that differentiate rootstocks are animportant tool to verify identity among these rootstocks during thevegetative propagation stage. The simple sequence repeat (SSR) markerPceGA59 was previously determined to uniquely distinguish thecommercially available GiSelA® rootstocks (Struss et al. 2002).

A targeted approach was used to develop a second SSR that was capable ofproviding differentiation of the rootstock selections of the inventionand others by the inventors. The approach used was based on the abilityto obtain genome-wide SNP (Single Nucleotide Polymorphism) data usingthe Illumina Infinium® cherry SNP array (Peace et al. 2012). An analysisof genome-wide SNP data for the rootstocks resulted in theidentification of a genomic region on linkage group 4 that was likely todiffer among the MSU rootstocks.

Using the peach genome sequence, an SSR marker was designed to targetthis region. This SSR marker, termed PruG4RS, successfullydifferentiated the MSU rootstocks. The development of PruG4RS and itscombined use with PceGA59 has successfully circumvented the limitationsof each individual marker and proven effective for use as a “qualitycontrol” DNA diagnostic tool for the commercial ‘GiSelA®’ rootstocks aswell as the MSU breeding program rootstock selections.

SSR MARKERS USED

Fingerprinting was performed using two simple sequence repeat (SSR)markers: PceGA59 and PruG4RS. The forward and reverse primers sequencesfor these two SSR markers are as follows:

TABLE 1 Primer name Primer sequence 5′ → 3′ PceGA59_redesigned_FTGAACCCCTCTACAAATTTTCC PceGA59_redesigned_R GACTGTAGAACCCAAAAGAACGPruG4RS - F TCAGAAAAGAAATTGCAACGGG PruG4RS - R CTT AGT GGT CTA GTC TGCATG C

The first primer pair, PceGA59, was published in Struss et al. (2002).However, the primer sequence reflects the addition of GC clamps. Basedon genetic data for the MSU cherry rootstocks we designed a secondprimer, PruG4RS (Andersen et al. 2015)

PLANT MATERIAL USED AND DNA EXTRACTION

Cherry DNA was extracted from young unfolded leaf blades using theprocedure of Edge-Garza et al. (2014).

POLYMERASE CHAIN REACTION (PCR)

PCR amplification was performed for the two SSRs using the followingconditions: 94° C. for 5 min followed by 9 cycles of 94° C. for 30 s,60° C. for 45 s (−1° C. per cycle), 72° C. for 1 min and then 24 cyclesof 94° C. for 30 s, 55° C. for 45 s, 72° C. for 1 min with an elongationstep of 72° C. for 5 min.

GEL ELECTROPHORESIS AND FRAGMENT VISUALIZATION

The PCR products were visualized by electrophoresis on a 6% denaturingpolyacrylamide gel in a 50 cm Sequi-Gen GT vertical sequencing apparatus(Bio-Rad Laboratories, Hercules, Calif.) for 2.5 hours at 70 watts with1× TBE buffer. Following electrophoresis, the gels were stained with theSilver Sequence DNA Sequencing System (Promega Corporation, Madison,Wis.) and dried for 24 hours. DNA fragment sizes were scored visuallyusing 10 and 50 base pair ladders (Invitrogen Corporation, Carlsbad,Calif.).

TABLE 2 DNA Fingerprint Data PceGA59 Allele (bp) 182 186 189 194 226‘Crawford’ + + + ‘Újfehértói + + + + Fürtös’ ‘GiSelA ® 6’ + + +‘Clare’ + + ‘Lake’ + + + PruG4RS Allele (bp) 172 182 190 192 196 198 200‘Crawford’ + + + ‘Újfehértói + + + Fürtös’ ‘GiSelA ® 6’ + +‘Clare’ + + + ‘Lake’ + + +

The following references for determination of various markers, arehereby incorporated in their entirety.

Struss D, Boritzki M, Karle R, and Iezzoni A F. 2002. Microsatellitemarkers differentiate eight Giessen cherry rootstocks. Hort Science 37:191-193.

Andersen K, Sebolt A, Stegmeir T, Iezzoni A. 2015. Development of theSimple Sequence Repeat marker PruG4RS for the differentiation of cherryrootstocks. American Society for Horticultural Sciences AnnualConference, New Orleans, La., August 4-7, Poster #023.

Edge-Garza, D., Rowland, T., Haendiges, S. and Peace, C. 2014. Ahigh-throughput and cost-efficient DNA extraction protocol for the treefruit crops apple, sweet cherry, and peach relying on silica beadsduring tissue sampling. Molecular Breeding 34:2225-2228.

The invention claimed is:
 1. A new and distinct variety of Cherry treerootstock named ‘Crawford’ substantially as described and illustratedherein.